Understanding Disparities in Obesity and Its Comorbidities in the U.S. Obesity/overweight has become a public health crisis in the U.S., and currently affects 2/3 of adults and 1/3 of children. Obesity can serve as a good indicator of unhealthy lifestyles such as unhealthy diet and inadequate physical activity (PA), two key modifiable risk factors for many chronic diseases including Type 2 diabetes (T2D) and hypertension (HBP). National data show large ethnic/SES disparities in obesity, T2D, HBP and healthcare. Obesity is believed as the result of a large number of biological, behavioral, social, environmental and economic factors and the complex interactions between them that promote a positive energy balance. The determinants of these disparities are still poorly understood. Many speculations have been made regarding the major contributors based on a growing body of literature, which has focused largely on individual factors such as SES, body image, and lifestyle factors and in some recent studies regarding selected community characteristics. Our understanding of the relative contribution of these factors, the interplay between them, and the social, economic and environmental context on individual-level behaviors is limited. Our proposed 3-year study is a systematic investigation based on data collected from national surveys, large cohort studies and other sources and aims to understand the causes of ethnic/SES disparities in obesity and its co-morbidities (T2D and HBP) as well as the related health care in the U.S., both adults and children. We will use an interdisciplinary approach to study the determinants at the individual-, family-, and community- level using several sophisticated statistical methods: Aim 1: To study the modifiable determinants of ethnicity/SES disparities in obesity and main co-morbidities. We will study the contributions (in absolute and relative terms) of risk factors at the individual-, family-, and community-level, including psychosocial, behavioral, environmental, economic, and policy factors. Aim 1a: Study the contribution of individual-level (e.g., diet, PA, SES, social support, psychosocial factors), and family-level variables (e.g., SES, participation in food assistance programs, resemblance between parents and their children in diet, PA, and weight status);Aim 1b: Study the contribution of social context factors (e.g., food outlets, fitness facilities, food prices, community characteristics, school PE and recess policies, school food service). Aim 1c: Consider all related factors at multi-levels simultaneously to study their relative contributions. Aim 1d: Using similar approaches study T2D and HBP. Aim 1e: Conduct ecological/ aggregated analysis to study the underlying causes of the disparities at the state and metropolitan statistical area (MSA) levels. Aim 2: To study the influence of primary healthcare on the disparities of obesity and the causes of health care (related to obesity) disparities. Aim 3: To conduct simulation analyses using systems analysis approaches to examine the effects of potential interventions and scenarios for helping eliminate the ethnicity/SES disparities. Findings of this study will help achieve several of the objectives specified in the NIH PAR, and help direct future interventions to eliminate health disparities. PUBLIC HEALTH RELEVANCE: The proposed 3-year study is a systematic investigation based on data from national surveys and other sources to understand the individual-, family-, and community-level causes of ethnic/SES disparities in obesity and its co-morbidities including type 2 diabetes and hypertension as well as the related health care in the U.S. using an interdisciplinary approach.